RF matrix switches are commonly used in telecommunications, typically in satellite downlink and uplink applications. They are used as physical layer switches to connect RF signal sources to their destinations. The incorporation of RF splitter or combiner circuits allows one signal source to be routed to multiple destinations or multiple signal sources to be routed to a single destination. Being able to make these connections on demand provides a great deal of flexibility in RF signal management and routing systems.
One trend over the past few years has been the need for large RF matrix switches with more than 64 inputs or outputs. However, large RF matrix switches have multiple issues. A single “one size fits all” system size which might be cost effective for a fully populated matrix may not be cost effective for an application with fewer than the maximum inputs and outputs. Expanding beyond the size of a single matrix module requires the use of many external expansion modules in addition to the multiple matrix modules. This quickly increases system cost and size. Large RF matrix switches have high power consumption, along with heat generation and noise pollution from the high-speed fans required to cool the unit.
Three-stage Clos network architectures are typically used to implement large RF matrices because they are more efficient and less costly than a full crossbar type architecture. The larger the matrix is, the larger the advantage of using a three-stage matrix architecture. However, the Clos architecture is relatively inefficient and more expensive for less than fully populated configurations. This is because regardless of the number of inputs or outputs, all of the middle stage matrix cards must be populated. Because it is common in many applications to have more outputs than inputs, a standard three stage square or symmetrical matrix will be a costly solution for many of these cases.
To date all commercially available 3-stage RF switch matrix implementations have used square or symmetrical block sizes, with the maximum number of inputs and outputs in a single chassis being the same. For applications that have more outputs than inputs one can build an asymmetric Clos network rather than a symmetric network. However, because of the relatively low volume of RF matrix switches it is not cost effective to build different chassis configurations specifically for different application sizes.
There is a need for an RF matrix switch which does not have these problems. Such a switch should be modular and able to be easily configured and reconfigured to implement multiple different matrix block sizes in the same chassis without having to change the backplane or basic configuration of the chassis, including the ability to reassign input and output card slots. This switch should also have the ability to implement reduced matrix block sizes in the standard chassis.
RF matrix switches typically use amplifiers biased for Class A operation to provide the maximum linearity and fidelity in the RF signal path. Unfortunately Class A operation requires the most power of the amplifier bias classes. The amplifiers in any active RF matrix switch account for the vast majority of the power consumed and heat generated in the system. For a large matrix module such as a 128×128 module, the power needed for amplifiers, the heat produced, and the cooling required become significant design and operation issues.
In most large RF matrix switch designs there are multiple amplifiers for any signal path. In the 3-stage Clos network in particular there are multiple paths available for any input to output connection, raising the probability of unused RF paths. The current state of the art is that RF matrix switches have all amplifiers on all the time regardless of whether they are being used or not by the signals passing through the matrix switch. They remain on because turning off an amplifier that is not being used can adversely affect the RF signal traveling through other amplifiers and paths in the switch. Keeping all amplifiers on all of the time produces high power consumption, along with associated heat generation and noise pollution from the high-speed fans required to cool the unit.
There is a need for a method and RF matrix switch in which amplifiers are actively managed to reduce power consumption without compromising RF performance. Active management of the amplifiers could greatly reduce power consumption and also reduce generated heat and the need for cooling.